Saltwater causing problems for Louisiana citrus growers

The recent drought situation in southern Louisiana is aggravating some serious problems in the citrus industry, but LSU AgCenter faculty members are working on potential methods to reduce the losses.

Since 1992, researchers and agents at the LSU AgCenter's Citrus Research Station near Port Sulphur, La., have been working to minimize the intrusion of salt into the root zone of citrus trees.

Commercial citrus production in Louisiana is conducted primarily in extreme southeastern Louisiana, but the proximity of the growing areas to the coast means the intrusion of saltwater also is an issue.

Wayne Bourgeois, resident coordinator at the LSU AgCenter's Citrus Research Station, says that while the problem of saltwater intrusion is an ongoing issue, it gets even worse during drought periods.

“The first symptoms came in the mid-1990s with that drought,” Bourgeois said. “The problem now is that there was little rain here this past January and February when other parts of the state got rain.”

The problems are now spread across much of Plaquemines Parish — the state's major citrus-producing area — and Bourgeois estimated that as much as 30 percent to 40 percent of the trees that are showing symptoms may die over time.

Salt invades the root zone of trees and concentrates until a little moisture comes along and helps it be absorbed by the trees. That, in turn, leads the trees to drop leaves. Rregular seasonal rains are neded to wash the salt out of the root zone.

Bourgeois said the Citrus Research Station is using a submersible sump pump to try to move some of the saltwater away from the trees at the station, but that's not a foolproof method of solving the issue.

“Our problem is that we don't know whether the salt is coming from the marsh or from the Mississippi River,” he said, adding, however, “We do know that when the river is low, it gets real salty.”

LSU AgCenter county agent Alan Vaughn of Plaquemines Parish said that during rainy years, the salt washes down below the root zone of the trees. In drought years, however, the problems are further aggravated by the lack of freshwater wells for irrigation.

The area's $9 million citrus industry as a whole is okay, but the saltwater is causing production to rise and fall.

“It takes several years after the salt washes down out of the root zone for the trees to get back to good health,” Vaughn said.

“The saltwater is reducing production by about 50 percent, because it causes good production one year and bad the next year,” Vaughn said. “This cycle is not allowing the industry to grow. We just continue to go through these up and down cycles.”

Vaughn said that a chloride level of 0.2 percent is known to be toxic to the trees, and that researchers are finding chloride levels as high as 1.6 percent in the parish.

Experts say the outcome of this year's crop comes down to how much rainfall is received to possibly wash some of the salt away.

“It's still too early to tell,” Bourgeois said. “Whatever fruit is left on the trees after the June drop is normally what makes the crop.”

Johnny Morgan (225-578-8484 or [email protected]) writes for the LSU AgCenter.

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